An ultrasonic diagnosis system acquires biological information by emitting an ultrasonic pulse and receiving a reflected ultrasonic wave from the object tissue. The ultrasonic pulse is generated in an oscillating element in an ultrasonic probe. The reflected ultrasonic wave depends on the acoustic impedance in the object tissue. The ultrasonic diagnosis system requires only a simple operation of bringing the ultrasonic probe into contact with the body surface of the object for displaying image data in real time. Thus, the system is widely used for morphologic and functional diagnosis of various organs.
In recent years, mechanically movable ultrasonic probes which has a one-dimensional array of oscillating elements, or ultrasonic probes which has a two-dimensional array of oscillating elements have enabled three-dimensional scanning of a diagnosis target part of the object. Three-dimensional image data or multi-planar reconstruction (MPR) image data can be generated from the three-dimensional data (volume data) acquired by the three-dimensional scanning and used for advanced diagnosis and treatment.
There have been proposed techniques of observing an inner surface of a lumen of an organ of an object by acquiring volume data concerning the lumen of the organ of the object by three-dimensional scan, setting a virtual viewpoint and a virtual view direction in the lumen of the organ, and producing virtual endoscopic (fly-through) image data representing the inner surface of the lumen of the organ viewed from the viewpoint (see Japanese Patent Laid-Open No. 2005-110973, for example).
According to these techniques, since endoscopic image data is generated based on the volume data externally acquired, invasion of the object during examination is significantly reduced. In addition, since the viewpoint and the view direction can be arbitrarily set in any lumens of organs including small alimentary canals and blood vessels to which an endoscope is difficult to insert, safe and efficient examination can be conducted with precision that cannot be achieved by conventional endoscopy.
By applying the process described in the above document to volume data acquired by an ultrasonic diagnosis system, virtual endoscopic image data can be observed in real time. Meanwhile, according to a common conventional method of setting a viewpoint and a view direction required to generate virtual endoscopic image data for volume data on a lumen of an organ, MPR image data comprising cross sectional images of the lumen of the organ formed by arbitrarily slicing the volume data is acquired, and the viewpoint and the view direction are set based on the MPR image data. However, in order to continuously observe the virtual endoscopic image data by moving the ultrasonic prove on the body surface of the object, the complicated process described above has to be repeated to update the viewpoint and the view direction as the ultrasonic probe moves. Thus, it is difficult to observe the virtual endoscopic image data in real time.
The present invention has been devised in view of the problem described above. An object of the present invention is to provide an ultrasonic diagnosis system that generates virtual endoscopic image data based on volume data acquired from an object and ensures constant observation of the virtual endoscopic image data in a preferred direction even when an ultrasonic probe moves, and an image data display control program.